Polymer brushes switch from soft to hard

An innovative way to modify the physical properties of polymers has been discovered by scientists in the UK.

Wilhelm Huck and colleagues at the University of Cambridge are designing materials that respond to their environment by investigating the behaviour of surface-tethered polyelectrolyte chains, known as polymer brushes, under various conditions.

polymer brushes switching from hard to soft matter

They saw that the stiffness of the positively charged polymer chains in solution greatly depends on the solvent. In water, the cationic polymer brushes adopt an extended conformation and are easily deformed by applying a force with an atomic force microscope (AFM) tip.

In electrolyte solutions where the anions are strongly coordinated to the polymer chains the brushes become so rigid they cannot be indented by the AFM tip. This transition from soft to hard matter can be reversed by simply changing the solvent. It is hoped this discovery can be exploited to develop smart surfaces.